1. Field of the Invention
The present invention generally relates to spinal fixation and fusion systems. The invention also generally relates to an insertion guide used during the insertion of a spinal implant system, wherein the implant system is used for correction, fixation, and/or stabilization of the spine.
2. Description of the Related Art
Intervertebral disks that become degenerated due to various factors such as trauma or aging typically have to be partially or fully removed. Removal of an intervertebral disk can destabilize the spine, making it necessary to replace the vertebral disk to maintain the height of the spine and to fuse the spine. Spinal implants are often used to prevent collapse of the spine. In a typical spinal fusion procedure, an intervertebral disk is removed and implants are inserted in the disk space between neighboring vertebrae. The implants maintain normal disk spacing and help restore spinal stability.
The implants may be constructed of any biocompatible materials sufficiently strong to maintain spinal distraction including, but not limited to, bone, stainless steel, or inert metals. Implants are typically packed with bone graft or a synthetic bone graft substitute to facilitate spinal fusion. Implants may have a variety of shapes, which include, but are not limited to, threaded cylinders, unthreaded cylinders, and parallelepipeds.
An anterior spinal fusion procedure is often preferred to a posterior spinal fusion procedure. An anterior spinal fusion procedure may require less bone removal and muscle distraction than a posterior spinal fusion procedure. Also, an anterior spinal fusion procedure may involve less risk of nerve damage than a posterior spinal fusion procedure. In an anterior spinal fusion procedure, a surgical opening in the abdomen may be up to ten inches deep. A protective sleeve may be used during preparation and insertion of a spinal implant. The protective sleeve may serve to protect abdominal organs, blood vessels and other tissue during the spinal implant procedure. The sleeve typically extends above the surgical opening during use. The sleeve may maintain distraction of the vertebrae. Also, the sleeve may serve as an alignment guide for tool and implant insertion during the surgical procedure.
Protective sleeves typically have distractors on a distal end. Distractors are projections that may be inserted into a disk space during a spinal fusion procedure. The distractors may serve to achieve and maintain distraction of adjacent vertebrae. Distractors may also help to secure the protective sleeve to the spinal column during the procedure. Protective sleeves may have one tube or two parallel tubes. FIG. 1 shows a single-tube protective sleeve, and FIG. 2 shows a dual-tube protective sleeve.
FIG. 1 illustrates a single-tube protective sleeve 30 used in a spinal fusion procedure. A spinal fusion procedure involves the insertion of one or more implants in a disk space between two vertebrae. Protective sleeve 30 includes a substantially long, hollow tube 32, two distractors 34 on opposite sides of an end of the tube, and two spikes 36 (only one shown) on opposite sides of the end of the tube. Protective sleeve 30 is typically sufficiently long to allow access to a spinal column of a large patient during an anterior procedure. Protective sleeve 30 may also be used in a posterior spinal fusion procedure.
A spinal fusion procedure using implants typically involves the insertion of two implants that are bilaterally positioned in an intervertebral disk space. During an anterior procedure, the disk space is prepared by performing a discectomy and by distracting the vertebrae adjacent the disk space. A cap (not shown) is placed on end 38 of the protective sleeve 30 opposite distractors 34 to protect the end of the sleeve during insertion. Distractors 34 may then be hammered into the disk space by striking the cap with a mallet (not shown). Spikes 36 are hammered into disk bone on the vertebrae and help to stabilize protective sleeve 30 during the procedure. Distractors 34 serve to separate the adjoining vertebrae to approximately normal spacing.
After insertion, a hole is drilled in the disk space by inserting a tool with a reaming head attachment through tube 32 and rotating the tool until a predetermined depth is reached. In some procedures, the hole is then tapped by inserting a tool with tap head attachment through tube 32 and rotating the tool until a predetermined depth is reached. The top and bottom of the reamed and tapped hole may extend into the end plates of the adjacent vertebrae. After the hole is prepared, an implant may be inserted in the hole by attaching the implant to an implant insertion tool and inserting the implant through tube 32. For untapped holes, the implant may be hammered into the hole by striking the implant insertion tool with a mallet. For tapped holes, the implant may be threaded into the hole by turning the implant insertion tool. Then, the protective sleeve 30 may be removed.
If a second implant is to be inserted, the protective sleeve 30 is hammered in the disk space opposite the first implant and the procedure is repeated. Alternatively, the protective sleeve 30 may remain inserted in the disk space, and a second single-tube protective sleeve 30 may be inserted adjacent to the protective sleeve.
The optimal alignment and spacing of implants in a spinal fusion procedure may be determined before surgery. Achieving the predetermined alignment and spacing during surgery is often important for optimal fusing of the adjacent vertebrae. Protective sleeve 30 has characteristics that may make achieving alignment difficult. First, each of the two holes is aligned, reamed, and tapped in a separate procedure. It is often difficult to align and space the holes correctly. Second, the alignment of protective sleeve 30 must be maintained after insertion. Any slight movement of protective sleeve 30, which may act like a lever arm, may result in misalignment of the hole.
FIG. 2 illustrates a dual-tube protective sleeve 40 used in a spinal fusion procedure involving the insertion of two implants into a disk space. Protective sleeve 40 includes substantially long, hollow tubes 32, one or more distractors 34 and one or more spikes 36. Protective sleeve 40 is typically long enough to allow access during an anterior procedure to an intervertebral disk in a large patient. Spinal fusion using implants with protective sleeve 40 involves the insertion of two implants, bilaterally positioned in parallel in an intervertebral disk space. During an anterior procedure, the disk space is prepared by performing a discectomy and by distracting the vertebrae adjacent the disk space. A cap (not shown) is placed on the end 42 of protective sleeve 40 opposite distractor 34 to protect the sleeve during insertion. Distractor 34 is then hammered into the disk space by striking the cap with a mallet (not shown). Spikes 36 are hammered into disk bone on the adjacent vertebrae to help stabilize protective sleeve 40 during the procedure. Distractor 34 serves to separate the adjoining vertebrae to approximately normal spacing. After insertion, holes are reamed in the disk space by inserting a tool with a reaming head attachment through tubes 32 and rotating the tool until a predetermined depth is reached. In some procedures, the holes are tapped by inserting a tool with a tap head attachment through tubes 32 and rotating the tool until a predetermined depth is reached. The top and bottom of the reamed and tapped holes may extend into the end caps of the adjacent vertebrae. After the holes are prepared, implants are inserted in the holes by attaching the implants to an implant insertion tool and inserting the implants through tubes 32. For untapped holes, the implants are hammered into the hole by striking the implant insertion tool with a mallet. For tapped holes, the implants are threaded into the holes by turning the implant insertion tool. After both implants are inserted, protective sleeve 40 is removed.
FIG. 3 shows a representation of implants inserted into disk space 44 using a dual-tube protective sleeve 40. Spinal nerves in the spinal canal 46 are protected by dura 48. Nerves 50 extend from the spinal canal 46. Implants 52 are inserted between two vertebrae 54 (one shown). Care must be taken during insertion of the implants 52 to make sure that the implants do not impinge on the nerves 50.
Like single-tube protective sleeve 30, dual-tube protective sleeve 40 has characteristics that make it difficult to align the implants correctly. First, the alignment of protective sleeve 40 must be maintained after insertion. Any slight movement of sleeve 40, which may act like a lever arm, may result in misalignment of the hole. Second, the long parallel tubes make it difficult to angulate the two implants 52 relative to each other. Angulated implants may be the desired alignment in some spinal fusion procedures. Using a dual-tube protective sleeve 40 has the advantage that the surgical procedure is simplified because there is only one insertion procedure, as opposed to two insertion procedures for a single-tube protective sleeve 30.
Single- and dual-tube protective sleeves share some disadvantages. First, the sleeves are typically unitary members that are long enough to extend out of a ten-inch deep surgical opening after being hammered into place. To maintain alignment after insertion, the sleeve must be kept as motionless as possible. The sleeve tends to act like a lever arm, and any slight motion of the sleeve during the procedure may result in misalignment of the implants. The sleeve acting as a lever arm is particularly problematic when the sleeve is handed off during the surgical procedure from one member of the surgical team to another member of the surgical team.
A second disadvantage of protective sleeves is related to the first disadvantage. The sleeve is held in place only by the distractors and the spikes inserted in the disk space. This connection may not be very secure. Because the connection is not secure, the sleeve may have to be held by the members of the surgical team throughout the entire procedure to maintain proper alignment. As noted above, any slight movement can result in the misalignment of the implants.
A third disadvantage of protective sleeves is that they may afford minimal protection to surrounding tissues during a spinal fusion procedure. Major blood vessels, parallel the anterior surface of the spine for much of the spine""s lower length. These vessels may be retracted during the procedure. The interface between the distal end of the sleeve and the spinal column is typically not a perfect fit. Gaps may exist between the sleeve and the vertebrae. The presence of gaps creates the risk of drill bits, taps, and implants coming into contact with the blood vessels or other surrounding tissues during the procedure. Also, the blood vessels may be pinched between the sleeve and the vertebrae. A nick or cut to either the aorta or the blood vessels can be life threatening.
The above-mentioned methods and systems inadequately address the need to angulate implants in some spinal fusion procedures, the need to maintain precise alignment throughout the procedure, and the need to protect surrounding tissues during the procedure. It is therefore desirable that an improved method and system be derived for inserting spinal implants during a spinal fusion procedure.
A holder or base may be used to insert instruments and/or spinal implants into a disk space during a spinal fusion procedure. In an embodiment, distractors and tangs of a holder may be driven into an intervertebral disk space. The distractors and tangs may secure the holder to the spine during. In an embodiment, fasteners extending through a holder into the adjacent vertebrae may be used fix the holder to the spine. In another embodiment, distractors, tangs, and fasteners secure a holder to the spine. A flange may be placed around the holder to protect the surrounding tissue and blood vessels. Protective sleeves may be inserted into and may be removed from conduits in the holder. A portion of the sleeve may have a slot or a window, located adjacent to the top of the holder. The slot or window may serve as a view-port to provide increased visibility near the procedure site. Surgical instruments may be inserted through the protective sleeves and through the holder conduits to prepare the intervertebral space for an implant.
An embodiment of a holder includes a body, one or more conduits passing through the body from the top to the bottom, one or more distractors on the bottom of the body, and one or more tangs on the bottom of the body. The body may have a smooth outer surface with no sharp comers. In some embodiments, the body may be flared near the bottom to provide shielding for surrounding tissue. The flared bottom may provide room for optional fasteners to extend at oblique angles from the body of the holder. The flared body may also provide the holder with a stable base against the spinal column.
An optional flange may be provided that fits around the outer surface of the holder. The flange may provide shielding of soft tissue, such as blood vessels and organs, from cutting tools at the junction of the holder and the vertebral bodies. The flange may also prevent damage to soft tissues due to pinching of the soft tissue between the holder and the vertebral bodies. The flange may be made of a rigid or semi-rigid material. A portion of the flange may be made of an elastic material so that the flange may stretch over and slide down the holder. In one embodiment, the holder may include a rim for holding the flange in place after installation. In another embodiment, the holder may include a groove for holding the flange in place. In another embodiment, the flange has an elastic collar, which holds the flange in place against the holder.
In some embodiments, the inner surfaces of the conduits may contain shoulders to limit the insertion distance of protective sleeves in the conduits. Above a shoulder, a conduit may be sized to match the outer diameter of a protective sleeve. Below the shoulder, the conduit may be sized to match the outer diameter of instrument heads and implants to be used in the procedure. In some embodiments, the shoulder may include slots configured to engage distractors on protective sleeves; thus allowing the holder to be used with single-tube protective sleeves having distractors.
Embodiments of the holder may have non-circular conduits. The cross sectional shape of the holder conduits and the protective sleeves inserted into the holder may be any desired shape that allows for the insertion of spinal implants into a disk space. For example, the cross sectional shape of the conduits may be rectangular if the cross sectional shape of the spinal implants are generally rectangular. Other embodiments of the holder may have circular conduits or conduits which do not have a regular geometric shape. Embodiments of holders that have circular conduits may be constructed with conduits of different diameters to accommodate protective sleeves and implants of different diameters.
Embodiments of holders may be provided with non-parallel angled conduits. Non parallel conduits allow the insertion of implants at oblique angles to improve spinal fusion and to protect nerves posterior to the disk space. Other holder embodiments may have parallel conduits.
The distractors on the bottom of the holder body are projections that insert into a disk space during a spinal fusion procedure. The distractors may serve to achieve and/or maintain distraction of the adjacent vertebrae. The distractors may also secure the holder to the spinal column during the procedure. The distractors may be substantially wedge-shaped, and may include curved surfaces. The tangs on the bottom of the holder body may serve to maintain distraction, and may also maintain a parallel orientation of the vertebrae during the procedure. The tangs may also be substantially wedge-shaped, and may also include curved surfaces. Outer surfaces of the distractors and tangs may be serrated to secure the holder to adjacent vertebrae during a spinal fusion procedure.
In one embodiment, there is one distractor centrally located between two conduits; and two tangs, with one next to each conduit opposite the distractor. Curved inner surfaces on the tangs and curved surfaces on the distractor may serve as partially enclosed extensions of the conduits, and may help maintain alignment of the implant during a spinal fusion procedure.
In some embodiments, the body includes one or more fastener holes for the insertion of fasteners into vertebrae. The fastener holes may be angled so that fasteners inserted through the holes extend obliquely into adjacent vertebrae without damaging the vertebral endplates. The fasteners may pass through the end caps of the vertebrae into cancellous bone in the interior of the vertebrae. The fasteners may serve to substantially anchor the holder to the spine during the spinal fusion procedure.
The height of the holder, when inserted in a spine, may be substantially less than the length of a protective sleeve. During the spinal fusion procedure, a protective sleeve may be inserted into a holder conduit when needed and removed when not needed without affecting alignment. Removal of a protective sleeve from the holder decreases the likelihood of a protective sleeve being inadvertently used as a lever arm during the procedure. Removing a protective sleeve from the holder may increase visibility at the procedure site. Removing a protective sleeve may also allow for easy irrigation of the entire surgical site, including the holes being prepared for the implants.
The ability to remove the protective sleeves when not in use, the short profile of the holder, and the fastener anchoring system all help to maintain proper alignment during the insertion of implants in a spinal fusion procedure.